Upper Instrumented Vertebra Level Research Articles

Can semirigid fixation of the rostral instrumented segments prevent proximal junctional kyphosis in the case of long thoracolumbar fusions? A finite element study.

Proximal junctional kyphosis (PJK) is a relatively common complication following long instrumented posterior spinal fusion. Although several risk factors have been identified in the literature, previous biomechanical studies suggest that one of the leading causes is the sudden change in mobility between the instrumented and noninstrumented segments. The current study aims to assess the biomechanical effect of 1 rigid and 2 semirigid fixation techniques (SFTs) on developing PJK. Four T7-L5 finite element (FE) models were developed: 1) intact spine; 2) 5.5-mm titanium rod from T8 to L5 (titanium rod fixation [TRF]); 3) multiple rods from T8 to T9 connected with titanium rod from T9 to L5 (multiple-rod fixation [MRF]); and 4) polyetheretherketone rod from T8 to T9 connected with titanium rod from T9 to L5 (PEEK rod fixation [PRF]). A modified multidirectional hybrid test protocol was used. First, a pure bending moment of 5 Nm was applied to measure the intervertebral rotation angles. Second, the TRF technique's displacement from the first loading step was applied to the instrumented FE models to compare the pedicle screw stress values in the upper instrumented vertebra (UIV). In the load-controlled step, at the upper instrumented segment, the intervertebral rotation values relative to TRF increased by 46.8% and 99.2% for flexion, by 43.2% and 87.7% for extension, by 90.1% and 137% for lateral bending, and by 407.1% and 585.2% for axial rotation, in the case of MRF and PRF, respectively. In the displacement-controlled step, maximum pedicle screw stress values at the UIV level were highest in the case of TRF (37.26 MPa, 42.13 MPa, 44.4 MPa, and 44.59 MPa for flexion, extension, lateral bending, and axial rotation, respectively). Compared to TRF, in the case of MRF and PRF, the screw stress values were reduced by 17.3% and 27.7% for flexion, by 26.6% and 36.7% for extension, by 6.8% and 34.3% for lateral bending, and by 49.1% and 59.8% for axial rotation, respectively. FE analysis has shown that the SFTs increase the mobility at the upper instrumented segment and therefore provide a more gradual transition in motion between the instrumented and rostral noninstrumented segments of the spine. In addition, SFTs decrease the screw loads at the UIV level and hence could help reduce the risk for PJK. However, further investigations are recommended to evaluate the long-term clinical usefulness of these techniques.

Surgical outcome of minimal invasive oblique lateral interbody fusion with percutaneous pedicle screw fixation in the treatment of adult degenerative scoliosis

Oblique lateral interbody fusion is performed for lumbar spinal restoration and stabilization, without extensive paraspinal muscle damage or massive bleeding. This study aimed to confirm the radiological and clinical outcomes of minimally invasive oblique lateral interbody fusion (OLIF) with percutaneous pedicle screw fixation (PPSF) as treatment for adult degenerative lumbar scoliosis. Medical records of 40 patients with degenerative lumbar spinal deformities who underwent selective OLIF and PPSF at our hospital between April 2018 and February 2021 were retrospectively reviewed. The study population comprised 7 male and 33 female patients aged 55-79 years. Standing radiography was performed, and the coronal cobb angle, distance between the C7 plumb line and central sacral vertical line, sagittal vertical axis, pelvic tilt, lumbar lordosis (LL), pelvic incidence (PI), and difference between PI and LL (PI-LL) were measured. Coronal scoliosis was defined as a lumbar coronal plane curve of > 15°. All patients achieved statistically significant improvements in coronal and sagittal alignment. The coronal cobb angle was corrected from 18.82° to 11.52°, and the central sacral vertical line was reduced from 18.30 mm to 15.47 mm. The sagittal vertical axis was significantly reduced from 45.95 mm to 32.72 mm. In contrast, the pelvic tilt and LL were minimally changed. For subgroup analyses, patients were divided into the convex and concave groups according to the direction of coronal curve correction. Vertebral body rotation was superior in the convex group than in the concave group. Furthermore, we checked for asymmetric facet degeneration at the upper instrumented vertebra (UIV) level at 1 year postoperatively. Of the 22 patients who underwent more than 3 level fusion surgery, 8 patients were confirmed the postoperative asymmetric facet degeneration in above UIV. Minor complications occurred in 16 patients, who recovered without any problems. Revision surgery was not performed in all cases. Minimally invasive OLIF with PPSF has a lower risk of complications and favorable surgical outcomes in patients with adult degenerative lumbar scoliosis. Access from the convex side is advantageous for the correction of the rotated vertebra. Extending the UIV level to the neutral vertebra can reduce the occurrence of postoperative asymmetric facet degeneration.

Preoperative Less Right Shoulder Elevation Had a Higher Risk of Postoperative Shoulder Imbalance When Main Thoracic Curve Shows Higher Correction Regardless of the Upper Instrumented Vertebra Level for Patients with Adolescent Idiopathic Scoliosis Lenke Type 1.

This is a retrospective study. This study aimed to investigate the incidence of and risk factors for postoperative shoulder imbalance (PSI) in patients with Lenke type 1. PSI is a complication resulting in poor self-image and satisfaction in adolescent idiopathic scoliosis (AIS) patients. We examined the data of AIS patients with Lenke type 1 curves who underwent posterior fusion surgery in a retrospective manner. PSI was defined as a 2-year postoperative absolute radiographic shoulder height (RSH) of ≥2 cm. Patients were divided into two groups based on the presence of PSI and the level of their upper instrumented vertebra (UIV) (UIV at T2 or T3 [U-UIV] or UIV below T3 [L-UIV]). The radiographic parameters and clinical outcomes were compared, and the cutoff values of risk factors were identified by multivariate analysis. Of 104 patients, 21 (20.2%) had left shoulder elevation PSI. The PSI group had a significantly greater preoperative RSH (-5.1 mm vs. -14.3 mm) and main thoracic (MT) curve correction rate (77.3% vs. 69.1%) than the non-PSI group. The PSI incidence did not differ between the U-UIV and L-UIV groups. Multivariate analysis identified preoperative RSH and the MT curve correction rate as independent risk factors for PSI. The receiver operating characteristic curve analysis identified the preoperative RSH cutoff value as -6.5 mm and MT curve correction rate cutoff value as 76.9%. Even in AIS patients with Lenke type 1 curves, the incidence of PSI was relatively high (20.2%). Patients with preoperative lower right shoulder elevation (i.e., RSH >-6.5 mm) had a higher risk of PSI regardless of UIV level when the MT curve showed a higher correction rate (i.e., correction rate >76.9%).

Clinical Effect of Transverse Process Hook with K-Means Clustering-Based Stratification of Computed Tomography Hounsfield Unit at Upper Instrumented Vertebra Level in Adult Spinal Deformity Patients.

This study aimed to investigate the efficacy of transverse process (TP) hook system at the upper instrumented vertebra (UIV) for preventing screw pullout in adult spinal deformity surgery using the pedicle Hounsfield unit (HU) stratification based on K-means clustering. We retrospectively reviewed 74 patients who underwent deformity correction surgery between 2011 and 2020 and were followed up for >12 months. Pre- and post-operative data were used to determine the incidence of screw pullout, UIV TP hook implementation, vertebral body HU, pedicle HU, and patient outcomes. Data was then statistically analyzed for assessment of efficacy and risk prediction using stratified HU at UIV level alongside the effect of the TP hook system. The screw pullout rate was 36.4% (27/74). Perioperative radiographic parameters were not significantly different between the pullout and non-pullout groups. The vertebral body HU and pedicle HU were significantly lower in the pullout group. K-means clustering stratified the vertebral body HU ≥205.3, <137.2, and pedicle HU ≥243.43, <156.03. The pullout rate significantly decreases in patients receiving the hook system when the pedicle HU was from ≥156.03 to < 243.43 (p<0.05), but the difference was not statistically significant in the vertebra HU stratified groups and when pedicle HU was ≥243.43 or <156.03. The postoperative clinical outcomes improved significantly with the implementation of the hook system. The UIV hook provides better clinical outcomes and can be considered a preventative strategy for screw-pullout in the certain pedicle HU range.

56. Predictive models identify patient and surgical variables that synergistically produce an optimal outcome following adult spine deformity (ASD) surgery

<h3>BACKGROUND CONTEXT</h3> Identifying the components needed for an optimal adult spinal deformity (ASD) surgical outcome could help inform surgeons and improve ASD treatment. However, defining the components that create an optimal outcome for ASD surgery is challenging because outcome metrics depend on multiple perspectives. A patient may receive a technically successful complication-free surgery but may report dissatisfaction with the treatment outcome. Conversely, a patient may incur multiple postoperative complications with high societal cost but report satisfaction with the surgical outcome. <h3>PURPOSE</h3> (1) Define an "optimal" ASD surgical outcome by integrating outcome metrics from multiple perspectives, and (2) identify the patient-specific and surgical components of ASD treatment that surgeons can employ to improve ASD surgery by creating a model that predicts a multi-perspective "optimal" surgical outcome. <h3>STUDY DESIGN/SETTING</h3> Prospective, multicenter analysis. <h3>PATIENT SAMPLE</h3> ASD patients enrolled into a prospective multicenter study. <h3>OUTCOME MEASURES</h3> Scoliosis Research Society-22r questionnaire (SRS-22r), Oswestry Disability Index (ODI), postoperative complications. <h3>METHODS</h3> Surgically treated ASD patients prospectively enrolled into a multicenter study from 2009-2018 were assessed at minimum 2-year follow-up for optimal outcome defined as (1) no major postoperative complication or complication requiring surgery, (2) patient reached MCID for ODI and SRS-22r subscore, and (3) patient satisfied and indicates would have the surgery again. Demographic, radiographic, PROM and surgical variables were assessed for associations with optimal outcome. Multivariate regression models were built based on level of upper instrumented vertebra (UIV) to identify variables that created a best fit predictive model for optimal outcome by R2 maximization and AIC/BIC minimization. <h3>RESULTS</h3> Of 1291 patients, 788 (mean 3.5 years follow-up), were eligible for study and evaluated. Optimal outcome patients (OP; n=196) had less preoperative opioid use (47.5% vs 56.8%) and fewer histories of prior spine surgery (65.4% vs 77.3%) than nonoptimal outcome (NO; n=592), respectively (p 0.05). Creation of the best fit predictive model for optimal outcome demonstrated synergy between several modifiable variables including preoperative BMI and opioid and tobacco use, final SVA and scoliosis, and use of supplemental rods and PJF prophylaxis. Refining the model for specific surgeries based upon UIV demonstrated increased synergistic impact of the modifiable variables and predictive accuracy (thoracolumbar UIV R2=0.41; upper thoracic UIV R2=0.77). <h3>CONCLUSIONS</h3> No single surgical or radiographic variable is independently predictive of an a priori defined multiperspective optimal outcome following ASD surgery. However, predictive modeling identified preoperative BMI, opioid and tobacco use, final SVA and scoliosis, and use of supplemental rods and PJF prophylaxis as variables surgeons can optimize and/or employ that act synergistically to predict an optimal ASD surgical outcome. Future research will focus on development of predictive models that highlight the synergistic effects of patient specific and interventional variables to improve surgical outcomes. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Evaluation of the Radiographic Risk Factors of Postoperative Shoulder Imbalance in Adult Scoliosis.

ObjectiveThis study aimed to evaluate the radiographic risk factors of postoperative shoulder imbalance (PSI) after adult scoliosis (AS) correction surgery.MethodsSeventy-nine patients with AS undergoing correction surgery at a single institution were reviewed. The mean follow-up was 28 months. Patients were divided into two groups based on their radiographic shoulder height (RSH): (1) the balanced group (RSH <10 mm) and (2) the unbalanced group (RSH ≥10 mm). The preoperative and postoperative Cobb angles of the proximal thoracic (PT), main thoracic (MT), thoracolumbar/lumbar (TL/L) and upper instrumented vertebra (UIV) were measured.ResultsNo significant difference was found between the balanced and unbalanced groups when the UIV was T1–2, T3–4, or below T4. Univariate analysis indicated that the unbalanced group had significantly higher postoperative RSH, lower percentage PT correction, and greater percentage MT correction. The classification and regression tree analysis revealed that when the correction percentage of PT curve was more than 55.3%, 84.4% of patients acquired shoulder balance. However, when the correction percentage of PT curve was less than 55.3%, and the correction percentage of MT curve was more than 56%, 65.7% of the patients developed PSI.ConclusionsIn AS correction surgery, a lower percentage correction of the PT curve and greater percentage correction of the MT curve were independent radiographic risk factors of PSI, regardless of the UIV level. Sufficient PT correction is required to achieve postoperative shoulder balance in AS correction surgery when the MT curve is overcorrected.

Should the upper end vertebra be selected as the upper instrumented vertebra in patients with Lenke type 5C adolescent idiopathic scoliosis?

Retrospective study. The upper end vertebra (UEV) is often selected as the upper instrumented vertebra (UIV) in patients with adolescent idiopathic scoliosis (AIS) with Lenke type 5C curves; however, the effect of adjusting UIV selection one level toward the cranial side (UEV + 1) is unknown. Therefore, this study aimed to assess the effect of UIV extension on scoliosis correction and global alignment in patients with the UIV as the UEV and UEV + 1. Data of 52 patients with AIS with Lenke type 5C curves who underwent selective thoracolumbar/lumbar (TL/L) fusion with a minimum follow-up period of 2years were retrospectively analyzed. The patients were divided according to the UIV in relation to the UEV: the UEV and UEV + 1 groups. Radiographic parameters and clinical outcomes were compared between the two groups. Among the 52 patients, 24 and 28 were included in the UEV and UEV + 1 group. Baseline data showed no intergroup differences except for the UIV level. While the UEV + 1 group showed a significantly greater TL/L curve correction (72.9% vs. 62.8%, p < 0.05) and a lower UIV tilt, it showed a significantly greater absolute value of radiographic shoulder height (RSH) (-7.9 vs. -0.9mm, p < 0.05) and coronal balance (-11.0mm vs -4.8mm, p < 0.05) at 2years postoperatively. The rate of post-operative shoulder imbalance (RSH ≥ 2cm) was significantly higher in the UEV + 1 than in the UEV group. No intergroup differences were observed in the sagittal alignment and patient outcomes between the two groups. When the UIV was selected as the UEV + 1, correction of the TL/L curve improved; however, it increased the risk of shoulder and coronal imbalance. There is no clinical benefit observed in terms of extending the UIV to the UEV + 1; therefore, the UIV should be selected as the UEV to maintain harmonious global alignment. Level 3.

Evidence Behind Upper Instrumented Vertebra Selection in Adolescent Idiopathic Scoliosis: A Systematic and Critical Analysis Review.

Level selection is often a dilemma in adolescent idiopathic scoliosis (AIS) surgery. The goals of selection of the upper instrumented vertebra (UIV) are to achieve the most optimal proximal balance of the shoulders, minimize any caudal problems due to proximal imbalance, and promote optimal sagittal balance. Several authors have proposed guidelines for selection of fusion levels in AIS. These guidelines are mostly expert opinions of distinguished surgeons in the field; they are not derived from clinical trials but rather from clinical acumen and many years of experience. We have systematically reviewed and critically analyzed the literature regarding UIV level selection in AIS surgery. The guidelines outlined by experienced surgeons seem to be supported by mixed or low-level evidence. Moreover, variation in studies may be due to lower levels of evidence and/or data that were insufficiently controlled for bias, confounding factors, and chance.

The effect of upper instrumented vertebra level (T9 vs T10) on radiologic and functional outcomes in the surgical treatment of adult spinal deformity in osteoporotic patients over 60 years of age

The effect of upper instrumented vertebra level (T9 vs T10) on radiologic and functional outcomes in the surgical treatment of adult spinal deformity in osteoporotic patients over 60 years of age

Risk Factors for Loosening of S2 Alar Iliac Screw: Surgical Outcomes of Adult Spinal Deformity.

Study DesignRetrospective study.PurposeTo determine the risk factors for S2 alar iliac (S2AI) screw loosening and its association with lumbosacral fusion in patients with adult spinal deformity (ASD).Overview of LiteratureS2AI screws have been widely used for ASD surgery in recent years. However, no studies have analyzed the risk factors for loosening of S2AI screws and its association with lumbosacral fusion.MethodsCases of 50 patients with ASD who underwent long spinal fusion (>9 levels) with S2AI screws were retrospectively reviewed. Loosening of S2AI screws and S1 pedicle screws and bone fusion at the level of L5–S1 at 2 years after surgery were investigated using computed tomography. In addition, risk factors for loosening of S2AI screws were determined in patients with ASD.ResultsAt 2 years after surgery, 33 cases (66%) of S2AI screw loosening and six cases (12%) of S1 pedicle screw loosening were observed. In 40 of 47 cases (85%), bone fusion at L5–S1 was found. Pseudarthrosis at L5–S1 was not significantly associated with S2AI screw loosening (19.3% vs. 6.3%, p=0.23), but significantly higher in patients with S1 screw loosening (83.3% vs. 4.9%, p<0.001). On multivariate logistic regression analyses, high upper instrumented vertebra (UIV) level (T5 or above) (odds ratio [OR], 4.4; 95% confidence interval [CI], 1.0–18.6; p=0.045) and obesity (OR, 11.4; 95% CI, 1.2–107.2; p=0.033) were independent risk factors for S2AI screw loosening.ConclusionsHigh UIV level (T5 or above) and obesity were independent risk factors for S2AI screw loosening in patients with lumbosacral fixation in surgery for ASD. The incidence of lumbosacral fusion is associated with S1 screw loosening, but not S2AI screw loosening.

Junctional kyphosis and junctional failure after multi-segmental posterior cervicothoracic fusion - A retrospective analysis of 64 patients.

Introduction:Junctional kyphosis (JK) and junctional failure (JF) are known complications after thoracolumbar spinal deformity surgery. This study aims to define the incidence and possible risk factors for JK/JF following multi-segmental cervicothoracic fusion.Methods:This is a retrospective analysis of 64 consecutive patients undergoing cervicothoracic fusion surgery, including at least five segments. Clinical and radiographic outcome measures were analyzed. A univariate analysis was performed to determine the effect of the level of upper instrumented vertebra (UIV) and lower instrumented vertebra (LIV), fusion status, C2 sagittal vertical axis (SVA), C2–C7 lordotic angle and T1 slope angle on the occurrence of JK/JF.Results:A total of 46 patients were followed up for a median of 1.1 years (range 0.3–4) with a median age of 65.5 years (range 42.2–84.5). Indication for surgery was spinal stenosis in 87%, trauma in 7%, and tumor in 6% of cases. The median number of levels fused was 7; the most frequent UIV was C2, and the most frequent LIV was T2. Solid fusion was achieved in 78% at the last follow-up. Postoperatively, the median C2 SVA was 32 mm (range − 7–75), median T1 slope angle was 33° (range 2°–57°), C2–C7 sagittal cobb angle was 4° (−29°–12°). JK developed in 4% of cases, no case of JF was observed. No statistically significant impact of bone density, level of UIV, level of LIV or postoperative sagittal parameters on the occurrence of JK/JF was observed, even though fusion status and pathologic T1 slope angle showed a trend toward significance.Conclusion:In this cohort of patients with mildly pathologic sagittal balance, JK was a rare event after multi-segmental fusion, observed in only 4% of cases. Neither level of UIV nor LIV had an influence on its occurrence; however, nonunion and pathologic sagittal alignment showed a nonsignificant trend.

The Amount of Relative Curve Correction Is More Important Than Upper Instrumented Vertebra Selection for Ensuring Postoperative Shoulder Balance in Lenke Type 1 and Type 2 Adolescent Idiopathic Scoliosis.

Retrospective review of a prospectively collected multicenter database. To assess how "overcorrection" of the main thoracic curve without control of the proximal curve increases the risk for shoulder imbalance in Lenke type 1 Adolescent Idiopathic Scoliosis (AIS). Postop shoulder imbalance is a common complication following AIS surgery. It is thought that a more cephalad upper-instrumented vertebra (UIV) decreases the risk of shoulder imbalance in Lenke type 1 and 2 curves; however, this has not been proven. Thirteen surgeons reviewed preop and 5-year postop clinical photos and PA radiographs of patients from a large multicenter database with Lenke type 1 and 2 AIS curves who were corrected with pedicle screw/rod constructs. Predictors of postop shoulder imbalance were identified by univariate analysis; multivariate analysis was done using the classification and regression tree method to identify independent drivers of shoulder imbalance. One hundred forty-five patients were reviewed. The UIV was T3-T5 in 87% of patients, with 8.9% instrumented up to T1 or T2. Fifty-two (36%) had shoulder imbalance at 5 years. On classification and regression tree analysis when the proximal thoracic (PT) Cobb angle was corrected more than 52%, 80% of the patients had balanced shoulders. Similarly, when the PT curve was corrected less than 52% and the main thoracic (MT) curve was corrected less than 54%, 87% were balanced. However, when the PT curve was corrected less than 52%, and the MT curve was corrected more than 54%, only 41% of patients had balanced shoulders (P = 0.05). This relationship was maintained regardless of the UIV level. In Lenke type 1 and 2 AIS curves, significant correction of the main thoracic curve (>54%) with simultaneous "under-correction" (<52%) of the upper thoracic curve resulted in shoulder height imbalance in 59% of patients, regardless of the UIV. This suggests the PT curve must be carefully scrutinized in order to optimize shoulder balance, especially when larger correction of the MT curve is performed. 2.

Scoliose idiopathique de l’adolescent Lenke 1 : influence du niveau de la vertèbre supérieure instrumentée sur l’équilibre sagittal du rachis cervical

BackgroundThis study aimed to evaluate the relationship between upper instrumented vertebra (UIV) level and cervical sagittal alignment (CSA) in Lenke 1 adolescent idiopathic scoliosis (AIS) patients, treated with posterior instrumentation. The hypothesis was that higher level of UIV would cause decreased cervical lordosis. MethodsSixty-three Lenke 1 AIS patients that underwent posterior fusion with pedicle screw instrumentation were retrospectively evaluated. Patients were divided into three groups according to UIV level (T2, T3, T4). Twenty patients without spinal deformity made up the control group. Patients were compared at two years follow-up according to radiographic changes in coronal and sagittal planes. Main sagittal parameters were C2-C7 cervical lordosis (CL), T1 slope, T1-T5 and T5-T12 kyphosis. Clinical outcomes were assessed using scoliosis research society (SRS)-22, short form (SF)-36 and neck disability index (NDI) questionnaires. ResultsPreoperative sagittal plane values of AIS patients were similar to the control group. C2-C7 CL, T1-T5 kyphosis and T1 slope significantly decreased postoperatively in T2 and T3 groups (p<0.05). These parameters were not changed significantly in T4 group after the surgery. T5-T12 kyphosis did not change significantly in all groups. SRS-22 and SF-36 scores significantly improved (p<0.05), while NDI scores were not changed significantly after the surgery. ConclusionsIn Lenke 1 AIS, treated with segmental all pedicle screw instrumentation using precontoured rods and rod rotation maneuver, postoperative decreased CL is more likely to occur if the UIV is selected as T2 or T3. Decreased CL seems to be caused by reduced T1-T5 kyphosis and T1 slope. However, the decrease in CL did not affect clinical outcome scores, including NDI, adversely. Hence, extending the fusion to appropriate level for shoulder balance seems reasonable. Level of evidenceIV.

Friday, September 28, 2018 10:30 AM–12:00 PM abstracts: deformity: technical factors: 171. The amount of curve correction is more important than upper instrumented vertebra selection for ensuring postoperative shoulder balance in Lenke type 1 adolescent idiopathic scoliosis

BACKGROUND CONTEXT Postoperative shoulder height imbalance is a common complication following adolescent idiopathic scoliosis (AIS) surgery. It is thought that a more cephalad upper instrumented vertebra (UIV) decreases the risk of shoulder imbalance in Lenke type 1 curves, however this has not been proven. PURPOSE To test the hypothesis that “over-correction” of the main thoracic curve without control of the proximal curve increases the risk for shoulder imbalance in Lenke type 1 AIS. STUDY DESIGN/SETTING Clinical photo and x-ray review of patients with Lenke 1 Main Thoracic AIS curves. PATIENT SAMPLE Surgically-treated patients with Lenke type 1 AIS were reviewed from a large multicenter database. OUTCOME MEASURES Postoperative shoulder height balance on clinical photos and PA radiographs. METHODS A total of 13 surgeons reviewed preop and 5-year postop clinical photos and PA radiographs of patients from a large multicenter database with Lenke type 1 AIS curves who were corrected with pedicle screw or rod constructs. Predictors of postop shoulder imbalance were identified by univariate analysis; multivariate analysis was done using the classification and regression tree (CART) method to identify independent drivers of shoulder imbalance. RESULTS A total of 145 patients were reviewed. The UIV was T3-T5 in 87% of patients, with 8.9% instrumented up to T1 or T2. 52 (36%) had shoulder imbalance at 5 years. On CART analysis: when the proximal thoracic (PT) Cobb angle was corrected more than 52%, 80% of the patients had balanced shoulders. Similarly, when the PT curve was corrected less than 52% and the main thoracic (MT) curve was corrected less than 54%, 87% were balanced. However, when the PT curve was corrected less than 52%, and the MT curve was corrected more than 54%, only 41% of patients had balanced shoulders (p=0.05). This relationship was maintained regardless of the UIV level. CONCLUSIONS In Lenke type 1 AIS curves, “over-correction” of the main thoracic curve (>54%) with simultaneous “under-correction” (

The effect of upper instrumented vertebra level on cervical sagittal alignment in Lenke 1 adolescent idiopathic scoliosis

This study aimed to evaluate the relationship between upper instrumented vertebra (UIV) level and cervical sagittal alignment (CSA) in Lenke 1 adolescent idiopathic scoliosis (AIS) patients, treated with posterior instrumentation. The hypothesis was that higher level of UIV would cause decreased cervical lordosis. Sixty-three Lenke 1AIS patients that underwent posterior fusion with pedicle screw instrumentation were retrospectively evaluated. Patients were divided into three groups according to UIV level (T2, T3, T4). Twenty patients without spinal deformity made up the control group. Patients were compared at two years follow-up according to radiographic changes in coronal and sagittal planes. Main sagittal parameters were C2-C7 cervical lordosis (CL), T1 slope, T1-T5 and T5-T12 kyphosis. Clinical outcomes were assessed using scoliosis research society (SRS)-22, short form (SF)-36 and neck disability index (NDI) questionnaires. Preoperative sagittal plane values of AIS patients were similar to the control group. C2-C7 CL, T1-T5 kyphosis and T1 slope significantly decreased postoperatively in T2 and T3 groups (p<0.05). These parameters were not changed significantly in T4 group after the surgery. T5-T12 kyphosis did not change significantly in all groups. SRS-22 and SF-36 scores significantly improved (p<0.05), while NDI scores were not changed significantly after the surgery. In Lenke 1 AIS, treated with segmental all pedicle screw instrumentation using precontoured rods and rod rotation maneuver, postoperative decreased CL is more likely to occur if the UIV is selected as T2 or T3. Decreased CL seems to be caused by reduced T1-T5 kyphosis and T1 slope. However the decrease in CL did not effect clinical outcome scores, including NDI, adversely. Hence, extending the fusion to appropriate level for shoulder balance seems reasonable. IV.

Shoulder balance in Lenke type 2 adolescent idiopathic scoliosis: Should we fuse to the second thoracic vertebra?

ObjectivesThere are many different systems recommending upper instrumented vertebra (UIV) for Lenke type 2 adolescent idiopathic scoliosis (AIS), several of which suggest that all Lenke type 2 AIS patients should be fused to the second thoracic vertebra (T2). However, all previously proposed UIV selecting systems do not accurately predict postoperative shoulder balance. We investigated whether fusing to T2 could prevent postoperative shoulder imbalance and identified circumstances under which to fuse up to T2. Patients and methodsWe retrospectively collected all patients with typical Lenke type 2 AIS who received surgery by one spine surgeon in our hospital from 2010 to 2014. Lateral shoulder balance was assessed utilizing radiographic shoulder height difference (RSH), coracoid height difference (CHD), clavicle-rib intersection difference (CRID), and clavicle angle (CA). Medial shoulder balance was assessed by T1 tilt angle and first rib angle (FRA). Lateral shoulders were considered to be level if the absolute value of RSH was less than 10 millimeters. All patients were divided into two groups as follows: 1) T2 group: UIV of T2 (n=49); and 2) below-T2 group: UIV of T3 (n=24) or T4 (n=6). Patients were assessed before surgery and at final follow-up with a minimum follow-up duration of 24 months. ResultsSeventy-nine typical Lenke type 2 AIS patients were identified. Preoperative CHD and CA were significantly associated with postoperative lateral shoulder imbalance (both p=0.045), whereas the UIV level was not significantly associated with it. Both fusing to T2 and to below T2 could improve RSH (p<0.001 and p=0.001, respectively). Fusing to T2 slightly worsened CHD, CRID, and CA at last follow-up (all p<0.001), while fusing to below T2 improved these lateral shoulder balance parameters (p=0.042, p<0.001, and p=0.007, respectively). For medial shoulder balance, fusing to below T2 worsened T1 tilt angle and FRA at last follow-up (p=0.025 and p<0.001, respectively), while fusing to T2 effectively kept these medial shoulder parameters in balance. In addition, for patients with an elevated left border of T1, the T2 group had worse preoperative T1 tilt angle but gained better postoperative T1 tilt angle than the below-T2 group (p<0.001 and p=0.040, respectively). ConclusionPreoperative lateral shoulder balance, more so than the UIV level, can strongly influence postoperative lateral shoulder balance. Fusing to T2 can only effectively improve medial shoulder balance, not lateral shoulder balance (CHD, CRID, and CA). Moreover, a positive T1 tilt angle is an indicator for fusing to T2 to improve medial shoulder balance.

Effect of the upper instrumented vertebral level (upper vs. lower thoracic spine) on gait ability after corrective surgery for adult spinal deformity

Background ContextThe relationship between gait pattern and the level of upper instrumented vertebra (UIV) in surgically treated patients with adult spinal deformity (ASD) has not been fully documented. PurposeThis study aimed to assess the effect of UIV level for the gait pattern in ASD. Study Design/SettingA prospective case series was carried out. Patient SampleThirty surgically treated consecutive female ASD with lumbosacral fusion (age 67.0±8.4 years; body mass index 22.7±2.4 kg/m2; Cobb angle 49.9°±21.3°; coronal vertical axis 1.5±3.6 cm; C7 sagittal vertical axis [C7SVA] 9.3±5.3 cm; pelvic incidence-lumbar lordosis 35.4°±25.8°; and lean volume of the lower leg 5.5±0.9 kg) were categorized into upper thoracic [UT] group or lower thoracic [LT] group based on the level of UIV (UT; UIV T2–T5, LT; UIV T9–T11), and the gait pattern were compared before and after corrective spine surgery. Outcome MeasuresScoliosis Research Society Patient Questionnaire, Oswestry Disability Index, and force plate analysis were the outcome measures. MethodsAll subjects underwent gait analysis on a custom-built force plate. Dual-energy X-ray absorptiometry. Subjects were followed-up for at least 2 years postoperation. ResultsThe UT group had larger baseline Cobb angle, whereas the LT group had larger C7SVA (UT vs. LT; Cobb angle: 59.2±22.9 vs. 44.6±17.4°, p=.03, C7SVA: 10.9±8.7 vs. 12.0±7.1 cm, p=.03). Preoperatively, no difference was found in gait velocity and stride between UT and LT group, whereas the right and left difference of step length was significantly large in UT group (velocity: 55.0±12.5 vs. 53.6±9.0 m/min, stride: 99.7±13.0 vs. 97.8±13.6 cm, step length; 10.4±4.9 vs. 5.6%±3.3%). Coronal and sagittal alignments were significantly improved in both groups (total; Cobb angle: 19.4°±10.6°, C7SVA: 5.3±2.9 cm, PI–LL: 12.1°±5.1°). Gait pattern, stride, and velocity all improved significantly after surgery (total; velocity: 62.3±8.9m/min, stride: 106.8±12.3 cm, p=.01). The knee angle at the heel contact phase and hip range of motion (ROM) were also significantly improved at postoperation (total; hip ROM: preoperation: 29.2°±9.1°, postoperation: 36.2°±4.8°, knee angle; preoperation: 10.6°±6.6°, postoperation: 4.4°±2.8°). No difference was observed for the pelvis and shoulder rotation on the horizontal plane at postoperation in both groups (total; pelvis rotation; preoperation: 7.4°±3.4°, postoperation: 7.9°±2.4°, shoulder rotation; preoperation: 7.4°±2.9°, postoperation: 8.7°±3.6°). The head vertical deviation was also not changed postoperatively in both groups (preoperation: 3.1±0.9 cm, postoperation: 3.1±0.8 cm). ConclusionsBoth UT and LT groups achieved similar improvement of gait ability and pattern after surgery. Additional studies will be needed to further define the effect of UIV for the activity of daily living such as fast walking, stepping the stairs, or standing from the chair in ASDs.

Proximal Junctional Kyphosis Following Posterior Hemivertebra Resection and Short Fusion in Children Younger Than 10 Years.

A retrospective study. To investigate whether proximal junctional kyphosis (PJK) or obvious proximal junctional angle (PJA) changes in the sagittal plane develops following short fusion in children younger than 10 years of age with congenital scoliosis, and to investigate the possible risk factors. PJK following long spinal fusion in adolescents and adults is a serious postoperative complication. Although the same problem may occur in patients with early-onset scoliosis who have undergone spine fusion, few studies have been reported any relationship between PJK and spinal fusion in young children with congenital scoliosis. Thirty-seven children treated in a single institution between 1998 and 2010 were reviewed retrospectively. The inclusion criteria included (1) younger than 10 years of age at the time of operation; (2) simple congenital deformity; (3) hemivertebra treated by posterior hemivertebrectomy with short fusion at a maximum of 5 motion segments; and (4) minimum follow-up for 2 years. The PJA from the caudal endplate of the upper instrumented vertebra (UIV) to the cephalad endplate of the vertebra adjacent to the UIV, thoracic kyphosis (T5-T12), lumbar lordosis (T12-S1), global sagittal balance, and magnitude of scoliosis of the major curves and upper compensated curves were measured on lateral radiographs. PJK was defined by a PJA>10 degrees during the follow-up and at least 10 degrees greater than the preoperative or early postoperative measurement. Wilcoxon tests were performed for statistical analysis. PJK occurred in 7 of 37 patients (18.9%), during an average of 4.5±3.2 years of follow-up (2-12 y). The UIV level of children with PJK was on T9 in 4 patients, and T11, T12, and L1 in 1. Screw malposition at UIV was confirmed by postoperative computed tomography images in 6 patients. Only 1 patient with a screw deviation did not develop PJK during the follow-up period. None of the patients with PJK was symptomatic, and no patients required revision surgery because of PJK. PJK occurred and progressed during the first 6 months after surgery followed by almost no progression or slight improvement in patients that could be followed up beyond 6 months postoperatively; in association with an increase of the lumbar lordosis. PJK occurred in pediatric patients with simple congenital deformities following hemivertebrectomy and short fusion. PJK was more common in patients with (1) greater immediately postoperative segmental kyphosis and PJA; (2) screw malposition on the UIV; and (3) hemivertebra located on the lower thoracic or the thoracolumbar region.

Posterior fossa decompression in Chiari I improves denervation of the paraspinal muscles

ObjectiveTo investigate whether posterior fossa decompression (PFD) could improve denervation of the paraspinal muscles in patients with Chiari I malformation (CMI).BackgroundParaspinal muscle denervation is one of the essential elements in...

Economic Impact of Revision Surgery for Proximal Junctional Failure After Adult Spinal Deformity Surgery: A Cost Analysis of 57 Operations in a 10-year Experience at a Major Deformity Center.

Retrospective cohort analysis. To evaluate the economic impact of revision surgery for proximal junctional failures (PJF) after thoracolumbar fusions for adult spinal deformity (ASD). PJF after fusions for ASD is a major cause of disability. Although clinical sequelae are described, PJF-revision operation costs are incompletely defined. Consecutive adults who underwent thoracolumbar fusions for ASD (August, 2003 to January, 2013) were evaluated. Inclusion criteria include construct from pelvis to L2 or above and minimum 6 months follow-up after the index ASD operation. Direct costs (surgical supplies/implants, room/care, pharmacy, services) were identified from medical billing data and calculated for index ASD operations and subsequent surgeries for PJF. Not included in direct cost data were indirect costs, charges, surgeon fees, or revision operations for indications other than PJF (i.e., pseudarthrosis). Patients were compared based on the construct's upper-instrumented vertebra: upper thoracic (UT: T1-6) versus thoracolumbar junction (TLjxn: T9-L2). Of 501 patients, 382 met inclusion criteria. Fifty-one patients [UT:14; TLjxn: 40 at index; average follow-up 32.6 months (6-92 months)] had revisions for PJF, which summed to $3.2 million total direct cost. Average direct cost of index operations for the cohort ($68,294) was significantly greater than PJF-revisions ($55,547). Compared with TLjxn, UT had a significantly higher average cost for index operations ($79,860 vs. $65,868). However, PJF-revision cases were similar in average cost (UT:$60,103; TLjxn:$53,920; P = 0.09). Costs of PJF amounted to an additional 12.1% of the total index surgical cost in 382 patients. Revision operations for PJF after long thoracolumbar fusions for ASD are associated with an average direct cost of $55,547 per case. Revision costs for PJF are similar based on the index procedure's upper-instrumented vertebra level. At a major tertiary center over a 10-year period, PJF came at a very significant economic expense amounting to $3.2 million for 57 cases. 3.